Antenna are used to radiate and/or receive typically electromagnetic signals, preferably with antenna gain, directivity, and efficiency. Practical antenna design traditionally involves trade-offs between various parameters, including antenna gain, size, efficiency, and bandwidth.
Antenna design has historically been dominated by Euclidean geometry. In such designs, the closed antenna area is directly proportional to the antenna perimeter. For example, if one doubles the length of an Euclidean square (or "quad") antenna, the enclosed area of the antenna quadruples. Classical antenna design has dealt with planes, circles, triangles, squares, ellipses, rectangles, hemispheres, paraboloids, and the like, (as well as lines).
With respect to antennas, prior art design philosophy has been to pick a Euclidean geometric construction, e.g., a quad, and to explore its radiation characteristics, especially with emphasis on frequency resonance and power patterns. The unfortunate result is that antenna design has far too long concentrated on the ease of antenna construction, rather than on the underlying electromagnetics.
Many prior art antennas are based upon closed-loop or island shapes. Experience has long demonstrated that small sized antennas, including loops, do not work well, one reason being that radiation resistance ("R") decreases sharply when the antenna size is shortened. A small sized loop, or even a short dipole, will exhibit a radiation pattern of 1/2.lambda. and 1/4.lambda., respectively, if the radiation resistance R is not swamped by substantially larger ohmic ("O") losses. Ohmic losses can be minimized using impedance matching networks, which can be expensive and difficult to use. But although even impedance matched small loop antennas can exhibit 50% to 85% efficiencies, their bandwidth is inherently narrow, with very high Q, e.g., Q&gt;50. As used herein, Q is defined as (transmitted or received frequency)/(3 dB bandwidth).
Applicant's above-referenced co-pending patent applications depict examples of fractal geometry, which geometry may be grouped into random fractals, which are also termed chaotic or Brownian fractals and include a random noise components, or deterministic fractals.
In deterministic fractal geometry, a self-similar structure results from the repetition of a design or motif (or "generator"), on a series of different size scales. One well known treatise in this field is Fractals, Endlessly Repeated Geometrical Figures, by Hans Lauwerier, Princeton University Press (1991), which treatise applicant refers to and incorporates herein by reference. Lauwerier notes that in its replication, the motif may be rotated, translated, scaled in dimension, or a combination of any of these characteristics. Thus, as used herein, second order of iteration or N=2 means the fundamental motif has been replicated, after rotation, translation, scaling (or a combination of each) into the first order iteration pattern. A higher order, e.g., N=3, iteration means a third fractal pattern has been generated by including yet another rotation, translation, and/or scaling of the first order motif.
Unintentionally, first order fractals have been used to distort the shape of dipole and vertical antennas to increase gain, the shapes being defined as a Brownian-type of chaotic fractals. See F. Landstorfer and R. Sacher, Optimisation of Wire Antennas, J. Wiley, New York (1985).
So-called microstrip patch antennas have traditionally been fabricated as two spaced-apart metal surfaces separated by a small width dielectric. The sides are dimensioned typically one-quarter wavelength or one-half wavelength at the frequency of interest. One surface is typically a simple euclidean structure such as a circle, a square, while the other side is a ground plane.
Attempting to reduce the physical size of such an antenna for a given frequency typically results in a poor feedpoint match (e.g., to coaxial or other feed cable), poor radiation bandwidth, among other difficulties.
Prior art antenna design does not attempt to exploit multiple scale self-similarity of real fractals. This is hardly surprising in view of the accepted conventional wisdom that because such antennas would be anti-resonators, and/or if suitably shrunken would exhibit so small a radiation resistance R, that the substantially higher ohmic losses O would result in too low an antenna efficiency for any practical use. Further, it is probably not possible to mathematically predict such an antenna design, and high order iteration fractal antennas would be increasingly difficult to fabricate and erect, in practice.
Thus, the use of fractals, especially higher order fractals, in fabricating microstrip patch antennas has not been investigated in the prior art.
Applicant's above-noted FRACTAL ANTENNA AND FRACTAL RESONATORS patent application provided a design methodology to produce smaller-scale antennas that exhibit at least as much gain, directivity, and efficiency as larger Euclidean counterparts. Such design approach should exploit the multiple scale self-similarity of real fractals, including N.gtoreq.2 iteration order fractals. Further, said application disclosed a non-Euclidean resonator whose presence in a resonating configuration can create frequencies of resonance beyond those normally presented in series and/or parallel LC configurations. Applicant's above-noted TUNING FRACTAL ANTENNAS AND FRACTAL RESONATORS patent application provided devices and methods for tuning and/or adjusting such antennas and resonators. Said application further disclosed the use of non-Euclidean resonators whose presence in a resonating configuration could create frequencies of resonance beyond those normally presented in series and/or parallel LC configurations.
However, such antenna design approaches and tuning approaches should also be useable with microstrip patch antennas and elements for such antennas. Thus, there is a need for a method by which microstrip patch antennas could be made smaller without sacrificing antenna bandwidth, while preserving good feedpoint impedance matching, and while maintaining acceptable gain and frequency characteristics.
The present invention provides such microstrip patch antennas, and elements for such antennas.